Introduction–
Signal transport between two different nodes is a fundamental building block for optical systems. Commonly symmetric between the nodes, such transport can be made directional in non-reciprocal devices such as isolator [1]}, circulator and directional amplifier [2]}, [3]}, [4]}, which undergoes growing interest and demand recently due to their potential utilities in signal processing and quantum networks [5]}, [6]}.
Conventionally, non-reciprocity is realized by incorporating magnetized materials which are not limited by the Lorentz reciprocity theorem.
Alternative magnetic-field-free schemes for non-reciprocal light transport include time modulation [7]}, artificial gauge fields [8]}, [9]}, reservoir engineering [8]}, [11]}, as well as various other approaches [12]}, [13]}, [14]}, [15]}, [16]}, [17]}. However, despite its importance for quantum information science and applications, the study of non-reciprocity in systems with demonstrated quantum properties has so far been limited to a handful of physical platforms, wherein the quantum correlations rely on the preparation of quantum states of atoms or photons [18]}, [19]}, [20]}.
